The present invention relates to apparatus for limiting access to an electrically controlled service to authorized users of the service. More specifically, the present invention concerns apparatus for enabling a security device which, when disabled, prevents unauthorized persons from gaining access to a service which is readily available to the user but for the impedance of the security device. The invention has numerous applications, as will subsequently be shown, one of which is in controlling access by television viewers to subscription television services.
Community antenna television (CATV) enables subscribers to receive an enhanced signal carrying television programs broadcast on standard television channels, typically over cables connected to viewers' receivers, for improved program reception. As an adjunct to the broadcast for publically available programming, CATV operators have offered pay TV services wherein subscribers are supplied with additional channels of TV programming, not publicly available, in return for payment of a fee which, depending on the nature of the subscription service, may be a periodic fee, e.g. monthly, or a single usage fee which entitles the viewer to television viewing of a specific channel of programming during a preselected time period. CATV services may include the provision of several channels of television viewing which may be individually or collectively made available to subscribers. For example, one channel of television viewing may include first run movies or live theater plays; another may provide sports events; while still another channel may provide a schedule of television programs not available on the public access channels.
In order to limit viewing of special programs to paying subscribers, it is necessary to be able to selectively enable and disable the apparatus which provides to each subscriber's television receiver, a signal suitable for viewing. As this cannot be feasibly done by having a technician from the CATV operator visit the subscriber's home before and after each program is viewed to perform the enabling and disabling operation, since it would be extremely costly, other methods of restricting access to TV programs are necessary. One approach to overcoming the need to send a technician to a subscriber's home is to enable and disable the subscriber's access to programming by remote control through the transmission of enabling and disabling signals to each subscriber's residence by complex transmitters and receivers and intermediary connecting lines. The apparatus required to accomplish remote control is complex and expensive and can only be feasibly used where there are a large number of subscribers among whom the cost of the equipment can be amortized over a period of time. The initial startup costs for assembling such a system and the uncertainty of the number of subscribers who can be expected to participate has discouraged smaller CATV operators from providing single program viewing services. Examples of systems which require the transmission of data from the CATV operator to the subscriber's television receiver are found in the U.S. Pat. No. 3,890,461 to Vogelman for a Ticket Operated Subscription Television Receiver and U.S. Pat. No. 4,058,830 to Guinet, et al for One Way Data Transmission System. The systems described in the foregoing patents rely on comparison between the transmitted data and data on a card furnished to the television subscriber.
It is also known that a magnetically encoded ticket or record medium can be used to actuate a switching device for energizing an electrical mechanism such as an electrically operated gate for permitting access to building or a depository in a bank. Such tickets, however, do not lend themselves to use for limited subscription television viewing since they can be re-used indefinitely and, hence, once supplied to a subscriber provide no way of limiting the time during which TV access permitted by the ticket or record medium can be obtained. One attempt to remedy this problem is disclosed in the aforementioned Vogelman patent which discloses the destruction of the information on the data ticket by destroying the ticket with a motor operated device.
It is also known in the art to employ a magnetic stripe to actuate a security device for enabling television viewing. Such a device is disclosed in U.S. Pat. No. 4,012,583 to Kramer for a pay TV control system which discloses a motel room key having a magnetizable stripe which permits a guest of the motel to gain access to television programs for viewing on a television receiver in his room. However, no information is encoded on the magnetizable stripe of the key in the Kramer patent so that the time of viewing or channels to be viewed cannot be selectively controlled.
Thus, while it is seen that the prior art includes devices for or adaptable to gaining access to subscription television services, those which can economically be provided only at a subscriber's television receiver are very limited as to flexibility in controlling time and channel access, while systems which permit greater flexibility are complex and expensive and require transmission of special information from the television broadcasting head end to subscribers in addition to the television viewing signals.